.NET Core Razor- New Roles assigned after registration

Question

I can assign a role at Registration level e.g Visitor, but how do I manage to change that role from User/Edit page? Also, how to add all the roles required to aspnetrole and then assign to users as needed? 

Model 

public class UserDataClass : IdentityUser
    {
        public string UserOrganization { get; set; }
        public string UserStatus { get; set; }
        public UserRoleList URole { get; set; }
        public ICollection<AppUserRole> UserRoles { get; set; }

    }

    public class UserRoleClass : IdentityRole
    {
        public string UsRole { get; set; }
    }

    public class AppUserRole : IdentityUserRole<string>
    {
        public virtual UserDataClass UsName { get; set; }
        public virtual UserRoleClass UsRole { get; set; }
    }

    public enum UserRoleList
    {
        Admin = 0,
        UserAdmin = 1,
        Management = 2,
        Visitor = 3
    }

 Registration - assign Visitor (working)

 

if (!await _roleManager.RoleExistsAsync("Visitor"))
                    {
                        var role = new IdentityRole("Visitor");
                        var res = await _roleManager.CreateAsync(role);
                        if (res.Succeeded)
                        {
                            await _userManager.AddToRoleAsync(user, "Visitor");
                            await _signInManager.SignInAsync(user, isPersistent: false);
                            _logger.LogInformation("A new account was created");
                        }
                    }

startup

 

services.AddIdentity<UserDataClass, UserRoleClass>(options => options.SignIn.RequireConfirmedAccount = true)
                .AddDefaultUI()
                .AddRoles<UserRoleClass>()